Ultrastructure studies of mitosis with special reference to the vesicles associated with the mitotic apparatus will be carried out using primarily marine invertebrate eggs. Descriptive studies of normal mitosis will be supplemented by experimental studies using various mitotic inhibitors and cytochemical techniques. The main objectives of the research are: To study the relationship of the vesicular component of the mitotic apparatus with other membrane systems of the cell, such as Golgi vesicles, nuclear membrane and annulate lamellae. To study the relationship of the vesicular component with the aster and spindle microtubules. To explore the possibility that the vesicles may somehow function in intracellular ionic regulation.